Method and apparatus for monitoring a data eye in a clock and data recovery system

Abstract

Methods and apparatus are provided for monitoring a data eye associated with a received signal. A plurality of samples of the received signal are obtained for each unit interval based on a clock recovered from the received signal, to obtain an estimate of the data eye. According to one aspect of the invention, the samples are obtained substantially simultaneous to a decoding of the received signal. The collected data eye samples can optionally be processed, for example, to collect statistics on the received signal or to determine a distribution of the received signal.

1 . A method for monitoring a data eye associated with a received signal, comprising: 
 obtaining a plurality of samples of said received signal for each unit interval based on a clock recovered from said received signal.    
   
   
       2 . The method of  claim 1 , wherein said obtaining step is performed substantially simultaneous to a decoding of said received signal.  
   
   
       3 . The method of  claim 1 , wherein said obtaining step further comprises the steps of sampling said received signal using a plurality of latches and estimating a value of said received signal by comparing values of said latches.  
   
   
       4 . The method of  claim 3 , wherein said plurality of latches sample said received signal by sampling said received signal for N steps within a unit interval.  
   
   
       5 . The method of  claim 3 , wherein said plurality of latches sample said received signal by sampling said received signal for M voltage levels.  
   
   
       6 . The method of  claim 3 , wherein said plurality of latches are clocked using said clock recovered from said received signal.  
   
   
       7 . The method of  claim 1 , wherein said obtaining step further comprises the steps of sampling said received signal using a sample and hold circuit to obtain a plurality of values of said received signal.  
   
   
       8 . The method of  claim 7 , further comprising the step of converting an output of said sample and hold circuit to a digital value.  
   
   
       9 . The method of  claim 1 , further comprising the step of collecting statistics on said received signal.  
   
   
       10 . The method of  claim 1 , further comprising the step of determining a distribution of said received signal.  
   
   
       11 . A circuit for monitoring a data eye associated with a received signal, comprising: 
 a plurality of latches for obtaining a plurality of samples of said received signal for each unit interval based on a clock recovered from said received signal.    
   
   
       12 . The data eye monitoring circuit of  claim 11 , wherein said plurality of latches obtain said plurality of samples substantially simultaneous to a decoding of said received signal.  
   
   
       13 . The data eye monitoring circuit of  claim 11 , wherein a value of said received signal is estimated by comparing values of said latches.  
   
   
       14 . The data eye monitoring circuit of  claim 13 , wherein said plurality of latches sample said received signal by sampling said received signal for N steps within a unit interval.  
   
   
       15 . The data eye monitoring circuit of  claim 13 , wherein said plurality of latches sample said received signal by sampling said received signal for M voltage levels.  
   
   
       16 . The data eye monitoring circuit of  claim 13 , wherein said plurality of latches are clocked using said clock recovered from said received signal.  
   
   
       17 . A circuit for monitoring a data eye associated with a received signal, comprising: 
 a sample and hold circuit for obtaining a plurality of samples of said received signal for each unit interval based on a clock recovered from said received signal.    
   
   
       18 . The data eye monitoring circuit of  claim 17 , wherein said plurality of samples are obtained substantially simultaneous to a decoding of said received signal.  
   
   
       19 . The data eye monitoring circuit of  claim 17 , further comprising a analog-to-digital converter to convert an output of said sample and hold circuit to a digital value.  
   
   
       20 . An integrated circuit, comprising: 
 a circuit for monitoring a data eye associated with a received signal, comprising means for obtaining a plurality of samples of said received signal for each unit interval based on a clock recovered from said received signal.    
   
   
       21 . The integrated circuit of  claim 20 , wherein said means for obtaining further comprises a plurality of latches and wherein a value of said received signal is estimated by comparing values of said latches.  
   
   
       22 . The integrated circuit of  claim 20 , wherein said means for obtaining further comprises a sample and hold circuit to obtain a plurality of values of said received signal.  
   
   
       23 . The integrated circuit of  claim 22 , further comprising a analog-to-digital converter to convert an output of said sample and hold circuit to a digital value.